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Full text of "Practical Organic Chemistry"

164               PRACTICAL ORGANIC CHEMISTRY
tap, so as to obtain small crystals of the hydrochloride. The
beaker is placed in a freezing mixture and the contents cooled
below 10. The sodium nitrite is added in small portions at a
time with stirring, the temperature being kept below 10. The
hydrochloride gradually dissolves in the form of the soluble
diazonium salt. Towards the end of the operation a drop of the
solution is occasionally tested with potassium iodide and starch
paper when an excess of nitrite is indicated by a blue sta.hi.
The solution is poured very slowly into the solution of caustic
soda previously cooled in ice, so that the temperature does not
rise above 10.
CH3.C6H4N2C1 + 2NaOH = CH3.C6H4N2ONa + NaCl + H2O.
Meantime the stannous chloride solution is converted into sodium
stannite by adding a 50 per cent, solution of caustic soda until
the precipitate of the hydrate nearly redissolves (about 30grams
of caustic soda). The liquid is placed in a round flask (500 c.c.)
attached to a condenser and cooled^in ice. The alkaline diazo
solution is poured through the top of the condenser in small
quantities at a time. After each addition there is a vigorous
effervescence and evolution of nitrogen,and a brown oil separates
which consists of impure toluene.
CH3CGH4NoONa + Sn(ONa)2 + H2O = CH3.C6H5 + No + NaoSnO.,
+ NaOH.
When the solution has all been added the toluene is distilled off
in steam, separated from the water, and dehydrated over calcium
chloride. It distils at 110. Yield 56 grams.
p. 284.
PREPARATION 64.
p-Cresol, CG
Griess, Annalen, 1866, 137, 39; Ihle, /. prakt. Chem.^ 1876,
H 451.
25 grms. /-toluidine.
2-5         cone, sulphuric acid (in 750 c.c. water).
20          sodium nitrite (in 40 c.c. water).
Mix the dilute sulphuric acid and toluidine in a large round
flask (ij litre) and cool to the ordinary temperature. The nitrite